Help with 3d cutting

[Nick McCombie]

Hello everyone!
I have a question regarding 3d cutting on the shopbot. Every piece I do has ridges in it where the ball nose end mill didn't cut. I have the stepover set at .08" with a .5" ball end mill. I have tried different stepovers and speeds, and nothing seems to work. I always just have to sand forever to get a smooth finish. This happens on blue insulating foam and recently on 3/4" MDF that was glued together. Thanks in advance!
Nick

[gc3]

might need to try a inside/outside or on with a offset profile cut with a .25 or .125 endmill afterwards. Are you talking about the "scope" at the ends of the relief?

[srwtlc]

A 0.5" ballnose is pretty big for 3D work unless you have a really large flowing design. You'll need to cut your stepover in half at least to clear up most of the ridges. Try 8% or 0.04". 6% or 0.03" would be better.

[myxpykalix]

try .25 bit with no more then a 9% stepover .08 is like 33%...??

[Brady Watson]

Pictures of your problem will yield faster & better answers

-B

[Nick McCombie]

We're using the .5" end mill because our parts are large so we need a 6" end mill to properly cut the piece out without the spindle hitting the piece, but it is a large flowing design with no small details. I'll take pictures tomorrow and post them. I guess I was just trying to rush it with the larger offset, I'll try the smaller offset tomorrow as well. Thanks for everyones quick responses!

[myxpykalix]

if you are doing a large piece you can use a larger bit (.5") but you will need to reduce your stepover to about what i said earlier.

[Christian]

Another one in agreement for reducing the stepover. If you don't want to do any sanding, go with 5% or less. It'll take forever, but save you time on the next step.